Geologic Timescale

Front

What is the Geologic Timescale?

Back

A system of chronological dating that relates geological strata to time, used to describe the timing and relationships of events in Earth's history.

Front

What does the Law of Superposition state?

Back

In an undeformed sequence of sedimentary rocks, the oldest layers are at the bottom and the youngest layers are at the top.

Front

What is a fossil?

Back

The preserved remains or traces of ancient organisms, often found in sedimentary rock.

Front

What can scientists learn from studying rock layers?

Back

They can determine the geologic history of an area, including the types of organisms that lived there and the environmental conditions.

Front

What is radiometric dating?

Back

A method used to date materials by comparing the abundance of a radioactive isotope to its decay products.

Front

What is the significance of the Cambrian Explosion?

Back

A period approximately 541 million years ago when a rapid diversification of life forms occurred, leading to the emergence of most major animal phyla.

Front

What is the difference between relative dating and absolute dating?

Back

Relative dating determines the sequence of events, while absolute dating provides a specific age or date for an event.

Front

What are index fossils?

Back

Fossils of organisms that were widespread but only existed for a short period, used to date and correlate the age of rock layers.

Front

What is the principle of faunal succession?

Back

Different layers of rock contain distinct groups of fossilized organisms, and these groups follow a recognizable order through time.

Front

What does the term 'geologic history' refer to?

Back

The record of the Earth's past, including the formation of rocks, the evolution of life, and major geological events.